1. Field of the Invention
This invention relates to a probe apparatus for inspecting electric characteristics of a plurality of semiconductor devices formed on a wafer. More particularly, the invention relates to a probe apparatus that can correct, on a real time basis, a positional change of a probe card, a positional change of a stage on which the wafer is put or the positional changes of both probe card and stage (contact position change) due to the influence of heat in case of inspecting in an environment such as high or low temperatures.
2. Description of the Related Art
A large number of semiconductor devices having the same electric element circuit formed therein are formed on a surface of a wafer. To inspect the electric characteristics of each electric element circuit before these electric element circuits are diced into individual semiconductor devices (chips), approval or rejection is judged by using a probe apparatus. The probe apparatus generally includes probing needles corresponding to each semiconductor device of the wafer and a probe card connected to a tester, and conducts electric measurement by bringing each probing needle into contact with each electrode pad of the semiconductor device while the probing needles are serially allowed to correspond to each semiconductor device of the wafer.
To conduct precise electric measurement, the probing needle of the probe card must be correctly brought into contact with the electrode pad of the semiconductor device. It is therefore necessary to control, very precisely, a stage on which the wafer is put and to correctly align the electrode pads to the probing needles before measurement is made. According to the prior art technology, a CCD camera is installed on the side of the stage on which the wafer is put, an alignment optical device is arranged at a position spaced apart from a test head to which the probe card having the probing needles is removably fixed, the distal end position of each needle is imaged and detected by the CCD camera while the wafer position and the chip pattern on the wafer are recognized by the alignment optical device and positioning between the electrode pad of a specific semiconductor device on the wafer and the probing needle is conducted by image processing, or the like.
It has been necessary in recent years to test the durability of the semiconductor devices and to test them in accordance with a use condition. Therefore, the test measurement of the semiconductor devices has been made in various measurement environments ranging from a high temperature environment of about 200° C. to a low temperature environment of about −55° C. In a probe apparatus in which a test measurement is made under a high temperature condition while a chuck mechanism of a wafer is heated, for example, a probe card so arranged in the proximity of the chuck mechanism as to oppose the chuck mechanism undergoes thermal expansion due to radiated heat from the chuck mechanism. However, because the probe card of the prior art is fixed at its periphery by a card retaining member, the probe card undergoes deformation in such a manner as to warp, as a whole, when thermal expansion occurs. When a measurement is repeated, deformation occurs in the probe card due to the contact pressure between the probing needle and the electrode pad. When the chuck (stage) portion is heated or cooled, the position of the chuck (stage) upper surface changes, too. Therefore, the contact position between the probing needle of the probe card and the electrode pad of the semiconductor pad deviates from the position of positioning before the measurement and their contact becomes insufficient. In consequence, the test measure cannot be made with high accuracy or the electrode pad is damaged due to an excessively strong contact.
FIG. 3 shows a change with time of the probe card from its normal temperature condition to its high temperature stable condition, that is, a typical example of the contact position change between the probing needle and the electrode pad with the passage of time. In other words, even when the contact position under the normal temperature condition is set to the reference position (zero position), the probe card, etc, undergoes thermal expansion due to the thermal influences under the measurement environment, the error of the contact position becomes drastically greater and the contact position change thereafter settles gradually to a stable condition.
To solve the problem of the contact position change due to heat, etc, counter-measures have been taken in the past by changing the material of a card holder of the probe card to the one that is not easily affected by heat under the measurement environment, or by measuring the probe position during the measurement to measure the positional change of the probe card (contact position change), or by starting the measurement after the probe card becomes thermally stable from the normal temperature condition to the temperature (high or low temperature) of the measuring environment.
However, the change of the material of the card holder to the material that is not easily affected by the influences of heat involves the problem that the material cost and the production cost increase.
When the distal end position of each probing needle is measured during the measurement and the contact position is corrected, the probing needle position must be confirmed by the CCD camera on the stage side. Therefore, as the probing needle is measured while being spaced apart from the heat source (stage), the measurement is conducted at a lower temperature than the temperature of the contact condition between the probing needle and the electrode pad, so that an accurate measurement result cannot be obtained. Because the distal end position of the probing needle must be re-measured while the probing needle is separated from the electrode pad every time, correction of the contact position is time-consuming.
Furthermore, when the measurement is started after the probe card is thermally stabilized, the through-put of the test measurement of the semiconductor devices drops and work efficiency becomes lower.
To detect the contact condition of the probing needle, the following technologies are known. The first technology detects variance of the tips of the probing needles by means of a laser beam and sets an optimum over-drive amount in accordance with this variance so that each probing needle can come into contact with the electrode pad at a suitable pressure (for example, Japanese Unexamined Patent Publication No. 7-161783). The second technology brings the probing needle into contact with the electrode pad, measures the capacitance between the electrodes so as to judge approval/rejection of the contact and controls the UP/DOWN distance of the wafer (for example, Japanese Unexamined Patent Publication No. 2000-68338). The third technology detects the contact condition between the probing needle and the electrode pad and corrects the fitting position of the probe card by means of a tilt/height adjustment mechanism (for example, Japanese Unexamined patent Publication No. 7-66249).
However, the technology of Japanese Unexamined Patent Publication No. 7-161783 does not detect, on a real time basis, the positional change of the probe card due to heat but detects the tip position of the probing needle while the probing needle is separated from the heat source (stage) in the same way as the technology described above that confirms the probing needle position by the CCD camera on the stage side. Therefore, a correct position measurement result cannot be obtained in a contact condition between the probing needle and the electrode pad. The technologies of Japanese Unexamined Patent Publication No. 2000-68338 and No. 7-66249 use the probe itself as the detection means. Therefore, the apparatus is likely to become complicated in construction and large in scale when hundreds or thousands of probing needles exist as in the case of a collective contact for measuring a single wafer by a single contact that has become the target in recent years.